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[TCP]: Fix two off-by-one errors in fackets_out adjusting logic 

1) Passing wrong skb to tcp_adjust_fackets_out could corrupt
fastpath_cnt_hint as tcp_skb_pcount(next_skb) is not included
to it if hint points exactly to the next_skb (it's lagging
behind, see sacktag).

2) When fastpath_skb_hint is put backwards to avoid dangling
skb reference, the skb's pcount must also be removed from count
(not included like above).

Reported by Cedric Le Goater <legoater@free.fr>

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilpo Järvinen 2007-10-07 23:36:41 -07:00 committed by David S. Miller
parent 182f6ed518
commit 29d0a309d1
1 changed files with 4 additions and 2 deletions
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6
net/ipv4/tcp_output.c
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@ -1755,14 +1755,16 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int m
if (tcp_is_reno(tp) && tp->sacked_out)
tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
tcp_adjust_fackets_out(tp, skb, tcp_skb_pcount(next_skb));
tcp_adjust_fackets_out(tp, next_skb, tcp_skb_pcount(next_skb));
tp->packets_out -= tcp_skb_pcount(next_skb);
/* changed transmit queue under us so clear hints */
tcp_clear_retrans_hints_partial(tp);
/* manually tune sacktag skb hint */
if (tp->fastpath_skb_hint == next_skb)
if (tp->fastpath_skb_hint == next_skb) {
tp->fastpath_skb_hint = skb;
tp->fastpath_cnt_hint -= tcp_skb_pcount(skb);
}
sk_stream_free_skb(sk, next_skb);
}